The effects of endogenous and dietary estrogens on colonic stem cells

描述（由申请人提供）：我们的数据支持内源性雌激素（E2）或含有雌激素化合物的化学保护饮食可降低结肠肿瘤发生风险的假设。这与人体研究一致，表明暴露于结肠中的雌激素可以防止恶性转化。虽然有与雌激素治疗有关的问题，膳食植物雌激素可能提供一个合适的替代品。事实上，流行病学数据表明，含有植物雌激素如染料木黄酮（Gen）的大豆可以降低结肠癌的风险。关于推定的靶点，结肠的“成体”体干细胞特别令人感兴趣，因为它们维持自我更新并且是癌症起始突变的靶细胞。最近的证据表明，正常的肠干/祖细胞可以启动结肠肿瘤的发生，并推动癌症向转移的进展。不幸的是，到目前为止，内源性和膳食雌激素对肠道干细胞信号传导的影响尚未确定。由于雌激素化合物可以影响调节结肠干细胞生态位和肿瘤演变的基因/介质，例如p53签名，我们的总体目标是进一步阐明E2和饮食Gen如何在恶性转化的不同阶段调节结肠干细胞。基于我们的实验结果，我们提出了两个具体的目标，以确定内源性（E2）和饮食雌激素（Gen）如何影响结肠中的多能干细胞。目的1将使用高度新颖的干细胞特异性Lgr 5-LacZ和Lgr 5-EGFP小鼠来量化暴露于内源性和饮食来源的雌激素后结肠癌发生的起始和肿瘤阶段结肠隐窝中干细胞、DNA损伤和靶向凋亡的数量和时空位置。目的2将使用Lgr 5-干细胞靶向的p53敲除小鼠（Lgr 5-EGFP-IRES-creERT 2 x p53 flox/flox）来确定p53在介导E2和Gen在肠干细胞中的作用中的分子作用。拟议的研究是高度创新的，将探索饮食雌激素化合物对结肠多能干细胞的生理作用。 公共卫生相关性：流行病学和临床数据表明，食用植物来源的膳食植物雌激素和/或暴露于内源性雌激素可降低女性患结直肠癌的风险。拟议的研究将确定以前未经测试的机制，饮食植物雌激素和内源性雌激素影响结肠干细胞群。从长远来看，这些研究将为开发新的饮食策略以降低结肠癌风险提供基础，并可能为预防结肠癌患者的肿瘤复发提供新的建议。

DESCRIPTION (provided by applicant): Our data support the hypothesis that endogenous estrogen (E2) or a chemoprotective diet containing estrogenic compounds reduce the risk of colon tumor development. This is consistent with human studies demonstrating that exposure to estrogen in the colon protects against malignant transformation. Although there are concerns related to estrogen therapy, dietary phytoestrogens may provide a suitable alternative. Indeed, epidemiological data suggest that soy, containing phytoestrogens such as genistein (Gen), reduces colon cancer risk. With respect to putative targets, "adult" somatic stem cells of the colon are of particular interest because they sustain self-renewal and are target cells for cancer initiating mutations. Recent evidence indicates that normal intestinal stem/progenitor cells can initiate colon tumorigenesis and drive cancer progression towards metastasis. Unfortunately, to date, the effects of endogenous and dietary estrogens on intestinal stem cell signaling has not been determined. Since estrogenic compounds can impact genes/mediators that regulate the colon stem cell niche and tumor evolution, e.g. p53 signature, our overall goal is to further elucidate how E2 and dietary Gen modulate colonic stem cells at distinct stages of malignant transformation. Based on our experimental findings, we propose two specific aims to determine how endogenous (E2) and dietary estrogen (Gen) impact multipotent stem cells in the colon. Aim 1 will use highly novel stem cell specific Lgr5-LacZ and Lgr5-EGFP mice to quantify the number and spatio-temporal location of stem cells, DNA damage and targeted apoptosis in the colonic crypt at the initiation and tumor stages of colon carcinogenesis following exposure to endogenous and diet-derived estrogens. Aim 2 will use Lgr5-stem cell targeted p53 null mice (Lgr5-EGFP-IRES-creERT2 x p53flox/flox) to define the molecular role of p53 in mediating the effects of E2 and Gen in intestinal stem cells. The proposed studies are highly innovative and will explore the physiological actions of dietary estrogenic compounds on multipotent stem cells in the colon. PUBLIC HEALTH RELEVANCE: Epidemiological and clinical data suggest that consumption of plant derived, dietary phytoestrogens and/or exposure to endogenous estrogen reduces the risk of colorectal cancer in women. The proposed studies will define previously untested mechanisms by which dietary phytoestrogens and endogenous estrogen influence stem cell populations in the colon. In the long-term, these studies will provide the basis for developing new dietary strategies for reducing colon cancer risk and may lead to new recommendations for prevention of tumor reoccurrence in colon cancer patients.